1. Field of Invention
The present invention relates to a thin film transistor in a liquid crystal display and, more particularly, to a method of precisely etching a layer when fabricating a thin film transistor in liquid a crystal display.
2. Discussion of the Related Art
FIG. 1A to FIG. 1C show cross-sectional views of a method of etching a layer according to a related art.
Referring to FIG. 1A, a layer 13 is formed by depositing a material, for example amorphous silicon, polycrystalline silicon, metal, silicon oxide, silicon nitride or the like on a substrate 11 by conventional fabrication processes, for example by chemical vapor deposition (CVD) or sputtering. The substrate 11 may be one of a number of materials, for instance transparent glass, a wire or an insulating layer on glass. The layer has an exposed surface 12 opposite the surface in contact with the substrate 11.
The surface 12 of the layer 13 is coated with photoresist, and a photoresist pattern 15 is defined by exposure and development to cover a predetermined portion of the surface of the layer. Commonly, an etch-resistant residue 17 is left on the surface 12 of the layer 13 outside the predetermined region. The residue 17 can be an undesireable by-product of the photoresist definition process, or it may result from adhesion of materials not intentionally introduced into the process, such as organic material present in the atmosphere.
Referring to FIG. 1B, a patterned layer 19 is formed by pattering the surface of the layer not covered by photoresist. Patterning processes include wet etch and dry etch, also called plasma etch. In each case, the photoresist pattern 15 acts as an etch mask.
Referring to FIG. 1C, the photoresist pattern 15 remaining on the now-patterned layer 19 and the residue 17 are removed.
Unfortunately, the related art is unable to provide a precisely patterned layer, e.g., a layer where all regions of the layer outside the predetermined region have been etched away. The presence of the unetched residue acts as an unintentional etch mask, causing undesired layer pattern artifacts to occur. Accordingly, there is a need for a method of precisely and completely etching a layer which prevents unintentional pattern artifacts from occuring due to the presence of undesired residues.